The invention relates to a semiconductor diode laser comprising a semiconductor body having a semiconductor substrate of a first conductivity type, on which there are successively disposed at least a first cladding layer of the first conductivity type, an active radiation-emitting layer and a second cladding layer of the second conductivity type, the semiconductor substrate and the second cladding layer being provided with current supply means, coherent electromagnetic radiation being produced in the active layer with a sufficiently high current intensity within an active region forming part of the active layer and located under a strip-shaped region, whose longitudinal direction is substantially perpendicular to a mirror surface located outside the active region, and a radiation-guide being located in an intermediate layer disposed between the mirror surface and the active region, which radiator optically couples the radiation-guiding layer to the mirror surface and is situated in a radiation-guiding layer lying between a third and a fourth cladding layer. The invention further relates to a method of manufacturing such a semiconductor diode laser, in which there are successively disposed on a semiconductor substrate at least a first cladding layer of the first conductivity type, an active radiation-emitting layer and a second cladding layer of the second conductivity type.
Such a semiconductor diode laser, which is of the so-called NAM (=Non-Absorbing Mirror) type, is particularly suitable for use as high-power semiconductor diode laser because also with high radiation powers produced, degradation of the mirror surface is low. Such a laser, in particular when manufactured in the GaAs/AlGaAs material system, is very suitable for use as writing laser in a system for optical recording, such as DOR (=Digital Optical Recording).
Such a semiconductor diode laser and such a method of manufacturing such a semiconductor diode laser are generally known from the article of H. Naito et al entitled "Highly reliable CW operation of 100 mW GaAlAs Buried Twin Ridge Substrate Lasers with Non-absorbing Mirrors" published in the Conference Digest of the 11.sup.th I.E.E.E. International Semiconductor Laser Conference, held from 29-8-'88 to 1-9-'88 in Boston (U.S.A.), Paper L-2, pp. 150-151. This article discloses a semiconductor diode laser, in which the radiation guide is formed in the intermediate region in the lateral direction by a step in the effective refractive index, absorption of part of the electromagnetic radiation produced occurring on either side of the radiation guide in a radiation-absorbing layer located within the amplification profile of the radiation produced. The radiation guide is formed in a radiation-guiding layer, which lies on the third cladding layer filling a groove in an absorbing layer. The known method utilizes LPE (=Liquid Phase Epitaxy) to provide inter alia the third cladding layer.
A disadvantage of the known semiconductor diode laser is that, as has been found in practice, with very high optical power degradation of the mirror can occur. This means that especially for the aforementioned applications, in which a high power emanating from the laser is desired, even more suitable semiconductor diode lasers are possible when the degradation of the mirror is further suppressed. The life and the power with which the laser can be used are favorably influenced thereby.